Re: [PATCH v7 00/11] extend task comm from 16 to 24

[Yafang Shao]

On Tue, Nov 2, 2021 at 9:18 AM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> On Tue, 2 Nov 2021 09:09:50 +0800
> Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
>
> > So if no one against, I will do it in two steps,
> >
> > 1. Send the task comm cleanups in a separate patchset named "task comm cleanups"
> >     This patchset includes patch #1, #2, #4,  #5, #6, #7 and #9.
> >     Cleaning them up can make it less error prone, and it will be
> > helpful if we want to extend task comm in the future :)
>
> Agreed.
>
> >
> > 2.  Keep the current comm[16] as-is and introduce a separate pointer
> > to store kthread's long name
>
> I'm OK with this. Hopefully more would chime in too.
>
> >      Now we only care about kthread, so we can put the pointer into a
> > kthread specific struct.
> >      For example in the struct kthread, or in kthread->data (which may
> > conflict with workqueue).
>
> No, add a new field to the structure. "full_name" or something like that.
> I'm guessing it should be NULL if the name fits in TASK_COMM_LEN and
> allocated if the name had to be truncated.
>
> Do not overload data with this. That will just make things confusing.
> There's not that many kthreads, where an addition of an 8 byte pointer is
> going to cause issues.
>

Sure, I will add a new field named "full_name", which only be
allocated if the kthread's comm is truncated.

> >
> >      And then dynamically allocate a longer name if it is truncated,
> > for example,
> >      __kthread_create_on_node
> >          len = vsnprintf(name, sizeof(name), namefmt, args);
> >          if (len >= TASK_COMM_LEN) {
> >              /* create a longer name */
>
> And make sure you have it fail the kthread allocation if it fails to
> allocate.
>
> >          }
> >
> >      And then we modify proc_task_name(), so the user can get
> > kthread's longer name via /proc/[pid]/comm.
>
> Agreed.
>
> >
> >      And then free the allocated memory when the kthread is destroyed.
>
> Correct.
>
> Thanks,
>
> -- Steve



-- 
Thanks
Yafang